Abstract: Currently, the approximate spin-density, Tl-, T2-weighted density MR Imaging are widely used in Clinical MRI. But unfortunately, because the density deferences between human soft tissues and tumors are not large enough, it's difficult to use these methods to distinguish different kinds of tumors. On the other hand, a large number of publications about " in vitro" NMR relaxation time measurments since 1970's have shown, that the NMR relaxation time of tumors are obviously different from that of human tissues, and it can be used to distinguish tumors.
The saturation recovery multi spin-echo method has been used to carry out the pure Spin-Lattice Relaxation Time Imaging. Using this method, one can also measure the in vivo Tl value point by point and the mean value of a special region, by means of ROI special software. Before doing the imaging experiments, the computer simulation of the physical-mathematical model has been done on VAX-11/785 and Micro VAX-Ⅱ systems.

Key words: MRI, Relaxation time T1